The video signal processing section of a television system may include provisions for decoding and displaying auxiliary video information such as closed caption data. Closed caption data includes ASCII digital data representing text corresponding the spoken audio information contained in a television signal. The closed caption data is displayed on the screen of the television system and is intended to provide a visible representation of the spoken portion of a television program as an aid to hearing impaired television viewers. In the United States, the closed captioning standard is set forth in Federal Communications Commission (FCC) regulations (see e.g., 47 CFR .sctn..sctn. 15.119 and 73.682). FCC regulations specify that digital closed caption data is to be transmitted in line 21 of field 1 in the video signal. Data representative of two ASCII characters is transmitted in each occurrence of line 21 of field 1. Future modifications to the standard may provide for closed caption data to select be located in other lines, e.g., line 21 of every field.
Closed caption data is obtained from the video signal by a decoder. The decoded signal is coupled to the video display when the closed captioning function is enabled by a hearing impaired viewer. A hearing impaired viewer may enable the closed captioning function by activating a switch (e.g., located on a remote control unit or on a control panel on the housing of the television system itself) or by selecting the closed captioning function from a menu displayed on the video screen during a control mode of operation. Once activated, closed captioning remains enabled until disabled by the viewer. A viewer that is not hearing impaired would tend to disable closed captioning function to avoid having the closed caption display interfere with the displayed video program.
A television system may also include an audio muting arrangement in the audio signal processing section. Activating the audio muting function causes the audio output from the television system to be disabled. The volume control setting is not affected so that when audio muting function is disabled, the normal audio output is reestablished without adjustment of the volume. Audio muting may be activated, for example, via a remote control unit.
Audio muting is useful in a variety of circumstances. For example, a user may wish to disable the audio output (i.e., enable muting) when answering the telephone or during a conversation. Although audio muting is useful under these circumstances, a viewer may undesirably miss important spoken information of the television program being viewed while the audio is muted.